Study the frequency, pathologic spectrum, and epidemiologic characteristics of benign and non-invasive breast disease inpopulations at low and high risk for breast cancer. Examine and compare benign breast lesions in three ethnic groups atdiffering risks for breast cancer, but living within one defined geographic area. Obtain incidence rates and histopathologic distributions of breast cancers for Anglos, Spanish Americans, and American Indians from the data of theNew Mexico Tumor Registry.